Integrated circuit edge protection method and apparatus

ABSTRACT

An apparatus, method, and system for providing a mechanical divider adapted to shield at least a portion of an active surface of an integrated circuit from out-gassing from underfill material. The mechanical divider is attached to a mounting substrate. The underfill material is dispensed on the mounting substrate. The integrated circuit is placed on both the mechanical divider and on the underfill material after the mechanical divider has been at least partially cured. The mechanical divider may include a base surface adapted to contact the mounting substrate, a lower wall surface extending upwardly from the base surface, an upper wall surface adapted to abut a side wall of the integrated circuit, and a ledge surface extending between the lower wall surface and the upper wall surface, the ledge surface adapted to contact at least a portion of the active surface of the integrated circuit.

CROSS-REFERENCES TO RELATED APPLICATIONS

This present application is a divisional of U.S. patent application Ser.No. 11/096,427 filed Mar. 31, 2005, and entitled “Integrated CircuitEdge Protection Method and Apparatus”. The specification of said patentis hereby incorporated in its entirety, except for those sections, ifany, that are inconsistent with this specification.

FIELD OF THE INVENTION

Disclosed embodiments of the present invention relate to the field ofintegrated circuits, and more particularly to integrated circuitpackaging.

BACKGROUND OF THE INVENTION

With the advancement of integrated circuit technology, the need tominiaturize integrated circuit packaging to meet the needs of thisintegrated circuit technology has increased exponentially. Thisrequirement has resulted in chip-scale packaging, wherein the ultimategoal is to have both the integrated circuit and the integrated circuitpackage be virtually the same size.

An integrated circuit package usually includes a mounting substrate andan integrated circuit, such as a semiconductor chip or die. Theintegrated circuit is located on or in the mounting substrate. One classof chip packaging includes integrated circuits that are produced withsolder contacts, on an active surface thereof, for purposes ofelectrically connecting the integrated circuit to solder deposits on themounting substrate. The term active surface of an integrated circuit, asused herein, means the surface which carries integrated circuitry. Theterm back surface, as used herein, means a side of the integratedcircuit that is positioned opposite and parallel planar with the activesurface.

During packaging, an epoxy underfill material is introduced into a spacebetween the integrated circuit and the mounting substrate and is curedthereafter. The epoxy acts to bond the integrated circuit to themounting substrate and to protect the solder contacts. The underfillmaterial that has been inserted between the integrated circuit and themounting substrate typically has a non-uniform profile. The non-uniformprofile is often due to the underfill material including both aninterstitial portion that is sandwiched between the integrated circuitand the mounting substrate, as well as a fillet portion that extendsdiagonally from the integrated circuit side walls to the mountingsubstrate.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are illustrated by way of example and notby way of limitation in the figures of the accompanying drawings, inwhich the like references indicate similar elements and in which:

FIG. 1 is a perspective view illustrating an electronic assembly, inaccordance with some embodiments of the present invention;

FIG. 2 is a cross sectional view taken along line 2-2 in FIG. 1illustrating an example electronic assembly, in accordance with anembodiment of the present invention;

FIGS. 3, 4, 5, 6, and 6A are cross sectional views taken along line 2-2in FIG. 1 illustrating the example electronic assembly of FIG. 2 atvarious stages of construction, in accordance with an embodiment of thepresent invention;

FIG. 7 is a cross sectional view taken along line 2-2 in FIG. 1illustrating an attachment of a mechanical divider in the exampleelectronic assembly of FIG. 2, in accordance with an embodiment of thepresent invention;

FIG. 8 is a cross sectional view taken along line 2-2 in FIG. 1illustrating an attachment of a mechanical divider in the exampleelectronic assembly of FIG. 2, in accordance with an embodiment of thepresent invention; and

FIG. 9 is a system including an electronic assembly in accordance withan embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

An apparatus, method, and system for providing a mechanical divideradapted to shield at least a portion of an active surface of anintegrated circuit from out-gassing from underfill material in anelectronic assembly is disclosed herein. In the following detaileddescription, reference is made to the accompanying drawings which form apart hereof wherein like numerals designate like parts throughout, andin which is shown by way of illustration specific embodiments in whichthe invention may be practiced. It is to be understood that otherembodiments may be utilized and structural or logical changes may bemade without departing from the scope of the embodiments of the presentinvention. It should also be noted that directions and references (e.g.,up, down, top, bottom, etc.) may be used to facilitate the discussion ofthe drawings and are not intended to restrict the application of theembodiments of this invention. Therefore, the following detaileddescription is not to be taken in a limiting sense and the scope of theembodiments of the present invention is defined by the appended claimsand their equivalents.

FIG. 1 illustrates a portion of an electronic assembly 10, in accordancewith one embodiment. The electronic assembly 10 may be a semiconductorpackage. The semiconductor package 10 may include an integrated circuit16 secured to a mounting substrate 14. The integrated circuit 16 may beformed in a rectangular piece of semiconductor material called a chip ora die. Examples of the semiconductor material include, but are notlimited to, silicon, silicon on sapphire, and gallium arsenide. In someembodiments of the present invention, the integrated circuit 16 may be aprocessor. For example, the integrated circuit 16 may be amicroprocessor.

FIG. 2 illustrates an example electronic assembly 10, in accordance withan embodiment of the present invention. In some embodiments of thepresent invention, a mechanical divider 18 may be located betweenintegrated circuit 16 and substrate 14. The mechanical divider 18 maycontact both the integrated circuit 16 and substrate 14. The mechanicaldivider 18 may be adapted to shield at least a portion of an activesurface 20 of the integrated circuit 16 from out-gassing from underfillmaterial. The mechanical divider 18 may be formed of any suitablematerial, according to the requirements of the particular application.Examples of materials suitable for forming the mechanical divider 18include, but are not limited to underfill materials such as epoxy andthe like.

The mechanical insert 18 may include a base surface 22 adapted tocontact the mounting substrate 14. A lower wall surface 24 may extendupwardly from the base surface 22. The lower wall surface 24 may bepositioned to surround a first layer of underfill material 26 as well asa solder joint 28 connecting the integrated circuit 16 to the mountingsubstrate 14. The first layer of underfill material 26 may be formed ofany suitable material, according to the requirements of the particularapplication. Examples of materials suitable for forming the first layerof underfill material 26 include, but are not limited to epoxy and thelike. Additionally or alternatively, the underfill material 26 may beformed as no flow underfill. Further, the mechanical divider 18 may beformed of the same or different material from the first layer ofunderfill material 26.

An upper wall surface 30 may be located above the lower wall surface 24.The upper wall surface 30 may be horizontally displaced relative to thelower wall surface 24 so as to lie in a plane separate from a plane ofthe lower wall surface 24. The upper wall surface 30 may be adapted toabut a side wall 32 of the integrated circuit 16. The upper wall surface30 may be adapted to minimize movement of the side wall 32 of theintegrated circuit 16 with respect to the mounting substrate 14.Additionally or alternatively, the upper wall surface 30 may be adaptedto align the side wall 32 of the integrated circuit 16 with respect tothe mounting substrate 14.

A ledge surface 34 may extend between the lower wall surface 24 and theupper wall surface 30. The ledge surface 34 may be adapted to contact atleast a portion of the active surface 20 of the integrated circuit 16.The ledge surface 34 may be adapted to fix the distance between theactive surface 20 of the integrated circuit 16 and the mountingsubstrate 14. Further, the ledge surface 34 may be adapted to minimizemovement of active surface 20 of the integrated circuit 16 with respectto the mounting substrate 14.

Additionally or alternatively, the ledge surface 34 may be adapted toshield at least a portion of the active surface 20 of the integratedcircuit 16 from out-gassing from the first layer of underfill material26. For example, the ledge surface 34 may contact and shield an edgeportion 36 of the active surface 20 of the integrated circuit 16 fromthe first layer of underfill material 26, while leaving an inner portion38 of the active surface 20 of the integrated circuit 16 open to thefirst layer of underfill material 26. The chemical reaction duringpolymerization of the first layer of underfill material 26 may result inout-gassing. This out-gassing may facilitate the formation of voidswithin the first layer of underfill material 26. In addition, thesevoids may be transported to an outer portion of the first layer ofunderfill material 26 near the edge portion 36 of the active surface 20of the integrated circuit 16 as pressure build-up occurs at the innerportion 38 of the active surface 20 of the integrated circuit 16. Theledge surface 34 may shield the edge portion 36 of the active surface 20of the integrated circuit 16 from the voids in the first layer ofunderfill material 26. Additionally or alternatively, the transportationof the voids from the first layer of underfill material 26 may belimited by locating the lower wall surface 24 adjacent the inner portion38 of the active surface 20 of the integrated circuit 16.

An outer wall surface 40 of the mechanical insert 18 may be positionedopposite the lower wall surface 24. The outer wall surface 40 may extendupwardly from the base surface 22. The outer wall surface 40 may bepositioned to be surrounded by a second layer of underfill material 42connecting the integrated circuit 16 to the mounting substrate 14.Accordingly, the mechanical insert 18 may be positioned between thefirst layer of underfill material 26 and the second layer of underfillmaterial 42. The second layer of underfill material 42 may be formed ofany suitable material, according to the requirements of the particularapplication. Examples of materials suitable for forming the second layerof underfill material 42 include, but are not limited to epoxy and thelike. Additionally or alternatively, the underfill material 42 may beformed as no flow underfill. Further, the second layer of underfillmaterial 42 may be formed of the same or different material from thefirst layer of underfill material 26.

FIGS. 3, 4, 5, 6, and 6A illustrate an example electronic assembly 10 atgiven stages of construction, in accordance with an embodiment of thepresent invention. A solder contact 44 may be formed on an upper surfaceof the mounting substrate 14 to face the integrated circuit 16.Similarly, solder deposit 46 may be formed on the bottom surface of theintegrated circuit 16 to face the mounting substrate 14. The soldercontact 44 and/or the solder deposit 46 may be formed as a solder ballor other suitable shape, according to the requirements of the particularapplication. For example, the solder deposit 46 may be formed as adimple-less bump having a concave shape. The lower wall surface 24 ofthe mechanical divider 18 may be adapted to form an opening to receivethe solder deposit 46 on the integrated circuit 16 as well as to receivethe solder contact 44 of the mounting substrate 14.

FIG. 4 illustrates an example electronic assembly 10 at a given stage ofconstruction, in accordance with an embodiment of the present invention.The mechanical insert 18 may be attached to the mounting substrate 14 byany suitable method. For example, FIG. 7 illustrates an exampleelectronic assembly 10 at a given stage of construction, in accordancewith an embodiment of the present invention, where a mold 48 dispensesand at least partially cures the mechanical insert 18 to the mountingsubstrate 14. After the mechanical insert 18 is dispensed and at leastpartially cured, the mold 48 may be removed. Alternatively, FIG. 8illustrates an example electronic assembly 10 at a given stage ofconstruction, in accordance with an embodiment of the present invention,where a placement tool 50 places a pre-formed and at least partiallycured mechanical insert 18 on the mounting substrate 14. After themechanical insert 18 is placed on the mounting substrate, the placementtool 50 may be removed. According to the requirements of the particularapplication, the mechanical divider 18 may be at least partially curedprior to the placing of the integrated circuit 16 on the first layer ofunderfill material 26; the mechanical divider 18 may be at leastpartially cured while attached to the mounting substrate 14; and/or themechanical divider 18 may be at least partially cured prior to attachingto the mounting substrate 14.

FIG. 5 illustrates an example electronic assembly 10 at a given stage ofconstruction, in accordance with an embodiment of the present invention.The first layer of underfill material 26 may be dispensed onto themounting substrate 14. The first layer of underfill material 26 may bedispensed within the lower wall surface 24 of the mechanical divider 18and below the ledge surface 34 of the mechanical divider 18.

FIG. 6 illustrates an example electronic assembly 10 at a given stage ofconstruction, in accordance with an embodiment of the present invention.At least a portion of the active surface 20 of the integrated circuit 16may be placed on the first layer of underfill material 26. For example,the inner portion 38 of the active surface 20 of the integrated circuit16 may be placed on the first layer of underfill material 26. At least aportion of the active surface 20 of the integrated circuit 16 may beplaced on the ledge surface 34 of the mechanical divider 18. Forexample, the edge portion 36 of the active surface 20 of the integratedcircuit 16 may be placed on the first layer of underfill material 26.

FIG. 6A illustrates an example electronic assembly 10 at a given stageof construction, in accordance with an embodiment of the presentinvention. Once integrated circuit 16 is placed on the mechanical insert18 and the mounting substrate 14, the second layer of underfill material42 may be dispensed on the mounting substrate 14. The second layer ofunderfill material 42 may contact one or both of the mechanical divider18 and a non-active surface of the integrated circuit 16, such as theside wall 32.

With reference back to FIG. 2, Once the second layer of underfillmaterial 42 is dispensed on the mounting substrate 14, reflow of thesolder deposit 46 (FIG. 6A) and the solder contact 44 (FIG. 6A) may beperformed. The reflow of the solder deposit 46 (FIG. 5) and the soldercontact 44 (FIG. 6A) creates the solder joint 28 connecting theintegrated circuit 16 to the mounting substrate 14. For example, thermalcompression bonding may be used to reflow of the solder deposit 46 (FIG.6A) and the solder contact 44 (FIG. 6A).

FIG. 9 illustrates a block diagram of one of many possible electronicsystems 60 in which embodiments of the present invention may be used.The electronic system 60 may utilize one or more embodiments of theelectronic assembly 10 described herein. As shown, the system 60includes a processor 62, such as an integrated circuit, and temporarymemory 64, such as SDRAM and DRAM, on high-speed bus 66. Voltageregulator 68 may be utilized to provide power to processor 62 via traces70. The high-speed bus 66 is connected through bus bridge 72 toinput/output (I/O) bus 74. I/O bus 74 connects permanent memory 76, suchas flash devices and mass storage device (e.g. fixed disk device), andI/O devices 78 to each other and bus bridge 72. In various embodiments,system 60 may be a set-top box, a digital camera, a CD player, a DVDplayer, a wireless mobile phone, a tablet computing device, or a laptopcomputing device.

Although specific embodiments have been illustrated and described hereinfor purposes of description of the preferred embodiment, it will beappreciated by those of ordinary skill in the art that a wide variety ofalternate and/or equivalent implementations calculated to achieve thesame purposes may be substituted for the specific embodiment shown anddescribed without departing from the scope of the present invention.Those with skill in the art will readily appreciate that the presentinvention may be implemented in a very wide variety of embodiments. Thisapplication is intended to cover any adaptations or variations of theembodiments discussed herein. Therefore, it is manifestly intended thatthis invention be limited only by the claims and the equivalentsthereof.

1. A method, comprising: attaching a mechanical divider to a mountingsubstrate, wherein the mechanical divider comprises a base surfacecontacting the mounting substrate; a lower wall surface extendingupwardly from the base surface; an upper wall surface integral to thelower wall surface; and a ledge surface extending between and integralto the lower wall surface and the upper wall surface; dispensing a firstlayer of underfill material on the mounting substrate; placing at leasta first portion of an active surface of an integrated circuit on thefirst layer of underfill material and a second portion of the activesurface on the ledge surface of the mechanical divider; abutting a sidewall of the integrated circuit to the upper wall surface of themechanical divider; and shielding at least a portion of the activesurface of the integrated circuit from out-gassing from the first layerof underfill material with the mechanical divider, wherein the ledgesurface is formed prior to placing the second portion of the activesurface of the integrated circuit on the ledge surface.
 2. The method ofclaim 1, further comprising at least substantially curing the mechanicaldivider prior to the placing of the first portion of the active surfaceof the integrated circuit on the first layer of underfill material. 3.The method of claim 1, further comprising at least substantially curingthe mechanical divider while the mechanical divider is attached to themounting substrate.
 4. The method of claim 1, further comprising atleast substantially curing the mechanical divider prior to attaching themechanical divider to the mounting substrate.
 5. The method of claim 1,further comprising dispensing a second layer of underfill material onthe mounting substrate, the second layer of underfill materialcontacting both a non-reactive surface of the integrated circuit and themechanical divider.
 6. The method of claim 1, wherein the dispensingcomprises dispensing the first layer of underfill material on themounting substrate within the lower wall surface of the mechanicaldivider.
 7. The method of claim 1, wherein the upper wall surfaceextends perpendicularly from the ledge.
 8. A method, comprising:attaching a mechanical divider to a mounting substrate, wherein themechanical divider comprises a base surface contacting the mountingsubstrate; a lower wall surface extending upwardly from the basesurface; an upper wall surface integral to the lower wall surface; and aledge surface extending between and integral to the lower wall surfaceand the upper wall surface; dispensing a first layer of underfillmaterial on the mounting substrate; placing a first portion of an activesurface of an integrated circuit on both the mechanical divider and onthe first layer of underfill material and a second portion of the activesurface on the ledge surface of the mechanical divider, wherein theledge surface is formed prior to placing the second portion of theactive surface of the integrated circuit on the ledge surface; andabutting a side wall of the integrated circuit to the upper wall surfaceof the mechanical divider.
 9. The method of claim 8, further comprisingat least substantially curing the mechanical divider.
 10. The method ofclaim 8, further comprises dispensing a second layer of underfillmaterial on the mounting substrate, the second layer of underfillmaterial contacting both a non-active surface of the integrated circuitand the mechanical divider.
 11. The method of claim 8, furthercomprising at least substantially curing the mechanical divider whilethe mechanical divider is attached to the mounting substrate.
 12. Themethod of claim 8, further comprising at least substantially curing themechanical divider prior to attaching the mechanical divider to themounting substrate.
 13. The method of claim 8, further comprisingfixing, by the mechanical divider, the distance between an activesurface of the integrated circuit and the mounting substrate.
 14. Themethod of claim 8, further comprising minimizing, by the mechanicaldivider, movement of the active surface of the integrated circuit withrespect to the mounting substrate.
 15. The method of claim 8, furthercomprising aligning, by the mechanical divider, the side wall of theintegrated circuit with respect to the mounting substrate.
 16. Themethod of claim 8, further comprising minimizing, by the mechanicaldivider, movement of the side wall of the integrated circuit withrespect to the mounting substrate.